In a projection image display system, an image projected by a projector is displayed by a member for projection image display. For example, in a head-up display system, which is one of projection image display systems, a member for projection image display, which has a function of a combiner capable of displaying simultaneously an image being projected and a scenery ahead, is used. In a head-up display system using a wind shield glass as the member for projection image display, a double image caused by reflection of projection light on the surface or rear surface of glass tends to become remarkable, and various solution methods have conventionally been tried.
For example, in Patent Literature 1, a method of forming, into a wedge-like shape, the cross-section of an intermediate film of a wind shield glass that is a laminated glass, to thereby cause images reflected from glass plates on the outside and inside of a car, respectively, to coincide with each other, is proposed. Many technologies for allowing p-polarized light to enter a glass surface, and for bringing, close to zero, reflected light from the surface of a member for projection image display while utilizing Brewster's angle, to thereby eliminate a double image, are known (for example, Patent Literature 2).